1. Technical Field
The present disclosure relates to substrate structures, and, more particularly, to a substrate structure for disposing electronic elements thereon.
2. Description of Related Art
Along with the rapid development of electronic industries, electronic products are developed toward the trend of miniaturization and multi-function. Accordingly, there have been developed various kinds of packaging modules.
FIG. 1 is a schematic cross-sectional view of a conventional packaging module 1. The packaging module 1 has a substrate structure 1′, an active element 8a and a passive element 8b disposed on the substrate structure 1′, and an encapsulant 9 encapsulating the active element 8a and the passive element 8b. 
The substrate structure 1′ has a first circuit layer 11, a plurality of first conductive posts 100 disposed on the first circuit layer 11, a first insulating layer 13 encapsulating the first circuit layer 11 and the first conductive posts 100, a second circuit layer 12 formed on the first insulating layer 13, a plurality of second conductive posts 15 disposed on the second circuit layer 12, a second insulating layer 14 encapsulating the second circuit layer 12 and the second conductive posts 15, a third circuit layer 16 formed on the second insulating layer 14, a plurality of conductive bumps 160 disposed on the third circuit layer 16, and an insulating protection layer 17 formed on the second insulating layer 14 and the third circuit layer 16. The conductive bumps 160 are exposed from the insulating protection layer 17, and a plurality of conductive elements 18 are disposed on the conductive bumps 160.
The active element 8a and the passive element 8b are electrically connected to the first circuit layer 11 through a plurality of conductive elements 19.
In the conventional substrate structure 1′, the first circuit layer 11, the first conductive posts 100 and the first insulating layer 13 constitute a wiring portion 1a; the second circuit layer 12, the second conductive posts 15 and the second insulating layer 14 constitute a wiring portion 1b; and the third circuit layer 16, the conductive bumps 160 and the insulating protection layer 17 constitute a wiring portion 1c. 
Generally, conductive through holes are formed for electrically connecting upper and lower circuit layers of a substrate. In the conventional substrate structure 1′, the first circuit layer 11 and the third circuit layer 16 are upper and lower circuit layers of the substrate structure 1′, respectively. As such, a portion of the first conductive posts 100 and the second conductive posts 15 can be viewed as conductive through holes 10 of the substrate structure 1′.
The substrate structure 1′ is a substrate having a high density of circuits and mainly applied in electronic products having high-end chips. As electronic products become smaller, more functional and faster and have higher storage capacity, high-cost high-end materials (for example, an insulating material having extremely small sized particles) are used to fabricate multi-layer circuit structures, for example, the three wiring portions 1a, 1b and 1c of FIG. 1, so as to form the substrate structure 1′ having a high density of circuits. In particular, the conductive traces of the substrate structure 1′ that are electrically connected to the active element 8a are fabricated through a fine-pitch circuit process and the fine-pitch circuit area A of the substrate structure 1′ that is used for disposing the active element 8a is made of a high-end material. That is, the particle size of the first insulating layer 13 and the second insulating layer 14 is extremely small, for example, less than 5 um.
However, since the non-fine-pitch circuit area B of the substrate structure 1′ that is used for disposing the passive element 8b is also made of a high-end material corresponding to the fine-pitch circuit area A, the overall fabrication cost of the substrate structure 1′ is increased.
Further, the substrate structure 1′ needs a plurality of wiring portions 1a, 1b and 1c for bonding with high-end chips, thus increasing the overall thickness of the substrate structure 1′.
Also, when the wiring portions 1a and 1b are stacked and aligned to form the conductive through holes 10, an alignment error likely occurs between the first conductive posts 100 and the second conductive posts 15, thereby adversely affecting the quality of the conductive through holes 10.
Therefore, how to overcome the above-described drawbacks has become critical.